Chemical treatment of shaped polymeric articles



United States Patent CHEMICAL TREATMENT OF SHAPED POLYMERIC ARTICLESRoger M. Schulken, Jr., and Harmon Long, Kingsport,

Tenn., assignors to Eastman Kodak Company, Rochester, N.Y., acorporation of New Jersey No Drawing. Filed May 21, 1958, Ser. No.736,688

8 Claims. (Cl. 1847.5)

This invention relates to a process for the aftertreatment of polymericarticles. More particularly this invention concerns a process for theafter-treatment of articles such as films and fibers which have beenformed from the sulfone acid-diol type of high polymer material whichremain substantially uncrystallized by any known heat treatment and yetare crystallized by treatment with certain organic liquids.

This application is a continuation-in-part of our application Serial No.474,276, now Patent No. 2,856,636.

In recent years considerable activity has been directed to themanufacture of formed articles from polymeric materials, particularlymaterials which are referred to herein as high polymers. For example,there are presently manufactured fibers, films and the like formedproducts from high polymeric materials, of which the so-calledterephthalic type of polyester is illustrative.

In fabricating such polymeric materials into articles, as for example inpreparing fibers, the polymer in the form of flakes or other particles,is melted under certain conditions and extruded or otherwise forcedthrough forming members to produce the article such as a fiber. Inmaking film, the polymeric material may likewise be melted and forcedthrough a die to form the film. Or, in some'instances, solutions of thepolymer may be made and the solution cast into films, spun into fibersor otherwise formed into shaped articles.

The products as first formed by the aforementioned extrusion or otherforming procedure, may not be espe cially suitable for use. Hense, suchinitially formed articles have been drawn or stretched at a temperaturein the range of 80-130 C. and then the formed product subjected to aheat treatment for heat setting or stabilizing ing processing at higherthan usual temperatures.

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2 of polymer may not only be suitably processed, but highly superiorformed products may be produced. That is, the formed products preparedin accordance with the present invention are tougher, have much higherheat distortion temperatures and otherwise exhibit improved properties.

This invention has for one object to provide a new process for theafteptreatment of high polymeric materials for imparting certainimprovements thereto. A particular object is to provide a process forthe aftertreatment of articles formed from non-heat-setting sultone-dioltype of high polymer. Still another-object is to provide a method forprocessing articles such as films and fibers which are formed from theaforesaid sulfonediol type of polymeric material. Still another objectis to provide a treatment applicable to formed articles of the aforesaidtype of polymer whereby the treated article is rendered tough, has highheat distortion temperatures, improved modulus and stiffness, and thelike. Still another object is to provide an after-treatment process forarticles formed from the high polymer of the class indicated whichincludes heating the formed article dur- Still another object is toprovide an improved after-treatment which includes a combination oftreating steps of heating and chemical treatment. Still a further objectis to produce an article formed of non-heat-setting sulfonediol polymer,which article possesses high modulus, high stiffness, high distortiontemperature and good dimensional stability. Other objects will appearhereinafter. As indicated above, we have found that the non-heatsettingsulfone-diol type of polymer with which the present invention isparticularly concerned, does not respond to the usual after-treatmentwhich is applied to many the formed article. Such heat treatment isquite frequently, I

applied to the formed article while the article is under tension orrestraint. For example, in the instance of a film or sheet which hasbeen stretched several hundred percent both longitudinally andlaterally, the film, while still under the tension of the tenteringapparatus, is subjected to the heat treatment.

There are certain types of high polymeric materials which we genericallyrefer to herein as non-heat-setting sulfone-diol polymers, which do notrespond to the type of after-treatment which has heretofore been used onmany high polymer materials. When such non-heat-set-' ting sulfone-diolmaterials are processed in the usual manner they have lower strengthproperties, are subject to embrittlement, craze on contact with certainliquids and have lower heat distortion temperatures. When these specialmaterials are stretched under ordinary conditions and then crystallized,they are extremely brittle.

It is, therefore, apparent that the development of an after-treatmentprocess which may be applied to the non-heat-setting sulfone-diol typeof polymer represents a highly desirable result. After investigation andexperimentation we have discovered a method whereby articles formed itemthe non-heat-setting sulfone-diol type polymers. The composition of someof the non-heatsetting sulfone-diol type of polymer which is used tomake the formed articles of the present invention, is illustrated by thefollowing:

(1) The polymer formed from reacting p,p'-dicarboxy diphenyl sulfone(sulfone acid) or derivative with 2,2- dimethyl-l,3-propanediol orderivative.

(2) A polymer similar to that in number 1 except 17 mole percent of thesulfone acid is replaced by a dicarboxylic acid such as terephthalic,isophthalic, o-phthalic, succinic, adipic, and sebacic.

(3) The polymer formed from reacting p,p'-dicarboxy diphenyl sulfonewith Z-methyl butanediol.

(4) A polymer similar to number 3 but modified by other diacids asinnumber 2.

(5) The polymer formed from reacting equal molar amounts of terephthalicacid or derivative and p,p'-dicarboxy diphenyl sulfone or derivativewith ethylene glycol or derivative.

Non-heat-setting sulfone-diol polymers have in common (a) the sulfoneacid and (b) one or more of the following glycols: (1) ethylene glycol,(2) Z-methyl butanediol, (3) 2,2-dimethyl-l,3 propanediol, and (4) otherglycols described more specifically elsewhere in this case. Certainother additives such as diacids or diols may be copolymerized with thesematerials. Each glycol decreases crystallizability and changes themelting temperature to a different extent. Thus, with respect to sulfoneacid-ethylene glycol polymer which melts so high as to render processingdiflicult some terephthalic acid may be added during polyesterificationto produce a polymer with a lower melting temperature. For example, formaking film or sheet, the sulfone component might constitute 25-100 molepercent. One or more dibasic acids such as terephthalic, isophthalic,4,4'-diphenyl dicarboxylic or the like might be present from a smallamount up to mole percent and sufiicient of the diol would be present toreact with the acids. Or,

lowing formula:

3' acids such as succinic, malonic (as 2,2-dimethyl malonic acid) whilebeing utilizable to 50 mole percent, in many instances would preferablybe present only up to 25 mole percent. a

The exact chemical composition per se of the type polymer describedherein as the non-heat-setting sulfonediol type polymer, and its methodof preparation, are not part of the present invention. However, we doconsider that our invention does extend to the combination of theprocess described herein as applied tosuch non-heatsetting Sulfone-dioltype polymers. For further completeness of disclosure, some additionalgeneral description will be set forth relative to the non-heat-settingsulfone-diol polymer compositions and their method of manufacture.

One process for preparing a linear polymer of the non-heat-settingsulfone-diol type comprises (A) condensing the desired mole proportions(say about 10 mole) of a p,p-sulfonyl dibenzoic diester having theformula:

(wherein R and R each represents a substituent selected from the groupconsisting of a p-hydroxyalkyl radical containing from 2 to 4 carbonatoms, an omega-hydroxyalkyl radical containing from 3 to 12 carbonatoms, and an alkyl radical containing from 1 to 6 carbon atoms, plusfrom about 1 to about 30 mole proportions of an aliphatic diesterselected from those having the following "formula:

6 R OOCl (CI-I -COOR (wherein t represents a positive integer of from 2to 18, inclusive, and R and R, each represents a substituent selectedfrom the group consisting of an omega-hydroxyalkyl radical containingfrom 2 to 12 carbon atoms and an alkyl radical containing from 1 to 6carbon atoms), with (B) a dioxy compound selected from ,the groupconsisting of those compounds having the fol- -(wherein R and R, eachrepresents a substituent selected from the group consisting of ahydrogen atom and an acyl radical containing 2 to 4 carbon atoms and Rrepresents an acyl radical containing 2 to 12 carbon atoms). be eitherbranched or cyclic in nature and branching must increase as the numberof carbon atoms increases. Branches should contain no more than ore, ortwo carbon atoms. The preferred range is 2 to 6 carbon atoms with thebranches such that the hydroxy and alkoxy groups are primary. The dioxycompound is employed in-such a proportion that there is at least anequivalent amount of oxy substituents in proportion to the carbalkoxysubstituents in the over-all combination of the diesters and the dioxycompound.

The condensation is carried out in the presence of a condensing agent inan amount of from about 0.005 to about 0.2% based on the weight of thediesters employed, selected from the group consisting of the alkalimetals, the alkaline earth metals, the oxides of these two groups ofmetals, the alkoxides containing from, 1 to 6 carbon atoms of these twogroups of metals, the carbonates and borates of these two groups ofmetals and lead oxide.

An elevated temperature is used andthe condensation is preferablyconducted in an inert atmosphere, the latter part of the condensationbeing con-' perature of from about 225 to about 310 C.

Another method of making the non-heat-setting sulfone-diol polymerbriefly is as follows: A prepolymer is made by treating the reactants asjust described for a' much shorter time. This prepolymer is ground to afine If R has more than 3 carbon atoms it must particle size. It is thenheated to a temperature of 200290 C. in a vacuum with stir-ing or in amoving stream of hot nitrogen until a suitablemolecular weight isreached.

However, irrespective of the particular method of preparing thenon-heat-setting sulfone-diol type of polymer, a suitable quantitythereof is obtained for fabricating into formed articles and processingin accordance with the present invention.

In the broader aspects of our invention we have found that thesulfone-diol polymeric material may be formed into the desired shape byany one of several procedures. For example, the non-heat-settingsulfone-diol polymer may be melt extruded directly into films or fibersusing standard equipment. However, we prefer in order to facilitate suchformation, to incorporate into the nonheat-setting sulfone-diol polymera content of various agents, exemplified by gamma-valerolactone, dibutylsebacate, or the like, which facilitates the (formation) extrusion ofthese high melting polymeric materials into shaped articles.

After extruding or otherwise suitably forming the non-heat-settingsulfone-diol type of polymer into a sheet, fibers or the like, theadditive for facilitating the formation is removed. One suitable methodfor removing the additive consists in submerging the formed article fora few seconds in mineral oil or a silicone oil first at around 160 C.and then at 220 C. The mineraloil used was of a type commerciallyavailable under the trade name Primol D. The silicone oil was DowCorning Silicone fluid No. 550. Such treatment removes the agent addedfor facilitating formation of the article and the product is now readyfor the further treatment in accordance with the present invention.

Rather than form the articles by melt formation as just described, it ispossible to form the polymer into articles by other procedures. Forexample, the non-heatsetting sulfone-diol type of polymer of the presentinvention may be placed in solution in trifluoroacetic acid or mixturesof trifiuoroacetic acid with tetrachlorethane or methylene chloride.Such solutions then may be converted into articles such as films orfibers in the usua way by casting on film forming surfaces or pumpingthrough spinnerettes.

The formed products, formed as aforesaid, are then preferably given arelatively high temperature heat treatment. For example, the formedproduct, such as sheet or film, is heated in air or mineral oil to about220-230 C. This will produce a tough, clear product. This result isunexpected since in heating other polymers such as polyester that farbelow their melting temperature, in most instances this increased theircrystallinity and made them brittle and hazy. However, in the presentinvention this heat treatment at the onset may be very important,particularly for solvent cast non-heat-setting sulfone-diol polymerfilms in order that the formed product may be readily further processedby stretching and the like.

The formed non-heat-setting sulfone-diol polymeric article, preferablyafter having been subjected to a heat treatment as just described, isnow ready for processing such as stretching. We have found that suchstretching operations are best conducted at somewhat higher than usualstretching temperatures. are used in the range of 135-190 C., about 165C. being a particularly useful temperature. These temperatures aresomewhat higher, as will be noted, than the -l30 C. frequently used inthe art for heating the polymeric material prior to stretching it.Within the preferred range of -190 C. of the present invention, theparticular temperature to use for any non-heatsetting sulfone-diolpolymer compositions will depend somewhat on the chemical compositionofthe polymer. A suitable estimate of the optimum temperature may be madeby determining at what temperature a film measurfer red to, exhibitsimproved properties.

'ing 1" x /8" by 0.005" as be easily stretched to four times itsoriginal length" with tweezers in an oil bath.

The temperature should not be high enough to cause the .the originaldimensions of the article being formed. That is, in making a fiber, theinitially formed product would be stretched two to six times itsoriginal length. In the instance of film, the stretchingmay not only belengthwise but across the width of the film.

After the shaped product has been stretched as aforesaid, a specialtreatment is applied to the non-heat-setting sulfone-diol polymercomposition employed herein. While the usual treatment applied toordinary polyesters is to heat set or stabilize them by heating thearticle at temperatures of about 150 C. under restraint, such treatmentwill not be operative in the present situation. We have found that thenon-heat-setting sulfone-diol type of polymer may not be set? by heatingat any between ten seconds and six minutes.

The finished shaped article of non-heat-setting sulfonediol polymerresulting from the chemical setting just re- Stretched films or fibershaving been subjected to a brief chemical treatment have relativelyhigher modulus, stitfness and heat distortion temperature as comparedwith usual polymeric materials treated by usual procedures. In furtherdetail, a film fully treated in accordance with the present inventionexhibits a heat distortion temperature of 230 C. as compared with onlyabout 175 C. for polyester processed in the usual manner.

The finished shaped articles in accordance with the present inventionalso have the advantage of greater reinvention, the cost of the finishedshaped product is lower.

It can be seen, in recapitulation, that in the broader aspects ourinvention comprises the following steps:

A. Subjecting the initially shaped article to an extractive or the liketreatment for removing agents which have been added to the polymer forfacilitating its initial formation into the shaped article,

B. The shaped article is then subjected to relatively high heating, forexample, at a temperature above 200 C. but somewhat below the melting orsoftening point of the polymer,

C. The shaped article is then stretched or draw along one or more axesat the relatively higher drawing temperature within the range of 135-490C.,

D. The drawn article is then set by exposure for a brief period toacetone, usually first to a vapor treatment and then by a liquidtreatment.-

The result of such treatment of non-heat-setting sulfonediol shapedarticles processed in accordance with the present invention is toproduce a superior article exhibiting improved heat distortionproperties and the like, as already pointed out above.

A further understanding of our invention will be had from aconsideration of the following examples which are set forth toillustrate the preferred embodiment of the instant invention.

EXAMPLE I A trifluoroacetic acid solution was made containing twentypercent of a polymer made from reacting p,p'-dicarboxy diphenyl sulfonecomponent (sulfone acid) with 2,2-dimethyl 1,3-propanediol component.This polymer had an, inherent viscosity of 0.7 to -40phenol-tetrachlorethane at 0.25% concentration.

This dope was coated to a film on a Teflon coated steel plate. Afterdrying, -'the film was quite brittle. However, on heating in a siliconeoil bath at 230 C. for a few minutes it became clear and tough. It wasthen stretched to six times its original length at 165 C. in thesilicone oil. It was then subjected to treatment with acetone vapor andthereafter with liquid acetone. A film quite tough in the direction ofstretch was obtained.

Still further examples of the instant invention are set forth in Table 1below. From this table it will be observed that a number of differenttypes of polymeric compositions of the present invention were extrudedinto film using standard equipment. These films were about 30 mil thickand 4" wide. The films were stretched one way and set under theconditions shown in Table l.

The properties of these films are also shown in Table 1. The heatdistortion temperature was determined by noting the point of 2% stretchwhen a film was heated usinf 55 lbs. per square inch tension. Resistanceto solvent hazing was determined by plunging a piece of the film inmethylene chloride. X-ray, density and birefringence were the standardmethods used for determining orientation and crystallinity. Toughnesswas determined in the direction of stretch. The temperature of stretchin air. is given and the ratio is that of the length of the unstretchedto the stretched film.

(Inherent viscosity 1.11.

In general when treating film in accordance with the present inventionwe prefer to apply both a first treatment with the chemical vapor and asecond treatment with the chemical in liquid state. Without the vaportreatment the liquid treatment alone may cause some haze to form on thesurface of the film.

Table 1 Stretch Resist- Heat Alter-Treatment ance to Distor- Orientedand Prod. Polymer echnique Film Quality Solvent tion Crystalline 0.)Ratio Hazing 'Iemp., Temp. 0.

Sulione acid with 17 mole percent 1.4 15sec. acetonevapor, then Toughclear..- Good.... 175 Yes.

succlmc acrd-pentanediol. 16 sec. in liqui then 0. 1 min. in air.Sulfone acid-2,2-dimethyl-1,3-prc- 100 1-6 --'..do Brittle hazy..- doCrystalized,

panediol. not

oriented. do 1-6 Tough clear rln 230 Yes. Same as B, except 17 molepercent 165 1-6 do do do 225 Yes.

sulfone acid replaced with terephthalic acid. Sulfone acid-2-methylbutauediol 145 1-6 do do do 200 Yes. Equimclar terephthalic and suifone145 1-6 do do do 220 Yes.

acids-ethylene glycol. Same as E 145 1-6 do do do 200 Yes.

Still further examples illustrating our invention are as follows:

EXAMPLE II A powdered polyester of the type described in Example I wasmixed with gamma valerolactone and extruded in conventional polyesterextrusion equipment into a filament. The gamma valerolactone was removedby passing the filament into a bath of Primol D at 160 C. and then intoanother bath at 220 C. This was done on a chilled roll so that thefilament did not distort. The filament was then stretched lengthwise at165 C. It was then exposed to acetone vapor for 15 seconds and then toacetone liquid for 15 seconds. The filament produced by this process wastough and had a heat distortion temperature of 230 C.

A filament was prepared by a similar treatment except it was stretchedat 125 C. This filament was brittle.

EXAMPLE HI A filament was extruded and processed as in Example 111except toluene vapor and liquid was used instead of acetone. Resultswere essentially the same.

It can be seen from the above examples that the heat distortionproperties are much improved by the stretching at the highertemperature, and by use of the nonheat-setting sulfone-diol polymer.

While in the above description we have referred in particular to theproduction of a shaped article such as film and fibers, other shapedarticles such as tubing, packaging boxes, etc. can be prepared. Theshaped articles produced in accordance with the present invention, suchas the film or sheets, may be used for photographic film base, wrappingmaterials and the like. As already mentioned, such shaped articlesexhibit improved properties, particularly with respect to high modulus,high stifiness, high heat distortion temperature and good dimensionalstability. The instant invention is also of particular importance inmany instances in that it permits use of polymeric materials which areof lower cost, and by means of the present invention may be made intoshaped articles having properties equal or superior to the properties ofpolymeric materials presently used for comparable purposes.

For convenience of reference, we may refer to the polymeric materialgenerically as non-heat-setting sulfonediol type. The various speciesthereunder, for convenience of reference, may be referred to asnon-heatsetting sulfone-diol dicarboxylic species, or succinic species,etc.

While the use of mineral oil or silicone oil has been 1 referred to forsome of the heating baths, various otherheating means such as air orWoods metal may be used. Although the temperature of ZOO-230 C. referredto is preferred, higher temperatures up to 250. C. may be used. Othersoftening agents such as dimethyl formamide may be used. Other changesmay be made such as various stretching mechanisms may be used and thefilms or fibers may be restrained in various types of clamps during thesetting treatment.

We claim:

1. The process of forming shaped articles of improved. properties fromnon-heat-setting sulfone-diol polymers which comprises forming thepolymer into a shaped article, subjecting the article to a relativelyhigh heating but below the melting point of the polymer, stretching theshaped article, and then setting the stretched, shaped article byexposure thereof for a short time to a chemical fluid consistingessentially of acetone.

2. The process of forming shaped articles of improved properties fromnon-heat-setting sulfone-glycol-terephthalic acid polymers whichcomprises forming the polymer into a shaped article, subjecting thearticle to a heating at above 200 C. but below the melting point of thepolymer, stretching the shaped article at a temperature within the rangeof 135-190 C. and then setting the stretched article in acetone.

3. The process of forming shaped articles of improved properties fromnon-heat-setting sulfone-diol polymer wherein the diol is a branchedchain diol, which comprises forming the polymer into a shaped article,subjecting the article to a heating at above 200 C. but below themelting point of the polymer, stretching the shaped article at atemperature within the range of 135- 190 C. and then setting thestretched article in acetone.

4. A process of forming shaped articles from'nonheat-settingsulfone-diol polymers which comprises dissolving the polymer in atrifluoro acetic acid solvent, forming a shaped article from thesolution, removing the trifluoro acetic acid solvent, subjecting thesubstantially -solvent free article to heating at about 220-230 C.,

stretching the articleat a temperature within the range 135-l90 C. andthen setting thestretched shaped article in acetone.

5. A process of forming shaped articles from nonheat-settingsulfone-diol polymers which comprises melting the polymer, extruding themolten polymer into the form of the desired shaped article, subjectingthe shaped article to stretching at a temperature within the range of135-190 C. and at a stretch ratio of 1:6, and then setting the'stretchedarticle by a short exposure to acetone vapors.

6. The process of forming shaped articles of improved properties fromnon-heat-setting polyester polymers which comprises forming the shapedarticle from said polymer, subjecting the shaped article to heating at atemperature above 200 C. but below the melting point of the polymet,drawing the shaped article and setting the drawn article by exposurethereof to a chemical fluid consisting essentially of acetone.

7. A process in accordance with claim 6 wherein the exposure is first toa vapor treatment followed by a liquid treatment.

8. In the process for the after-treatment of attenuated articles madefrom high polymers the improvement steps which comprise stretching saidarticles and then treating the stretched article in a chemical fluidconsisting essentially of acetone.

References Cited in the file of this patent UNITED STATES PATENTS FranceJune 3, 1954

4. A PROCESS OF FORMING SHAPED ARTICLES FROM NONHEAT-SETTINGSULFONE-DIOL POLYMERS WHICH COMPRISES DISSOLVING THE POLYMER IN ATRIFLUORO ACETIC ACID SOLVENT, FORMING A SHAPED ARTICLE FROM THESOLUTION, REMOVING THE TRIFLUORO ACETIC ACID SOLVENT, SUBJECTING THESUBSTANTIALLY SOLVENT FREE ARTICLE TO HEATING AT ABOUT 22-230*C.,STRETCHING THE ARTICLE AT A TEMPERATURE WITHIN THE RANGE 135-190*C. ANDTHEN SETTING THE STRETCHED SHAPED ARTICLE IN ACETONE.